Web tracking is the activity of a website to track and engage its visitors by pushing advertising and content, and to analyze visitor behavior. Web tracking is generally performed by software, such as Javascript, that is embedded in a web page, e.g., the Javascripts shown below appear in a CNN International web page. Portions of the Javascripts are underlined, showing various trackers from Twitter, Facebook, Google and many others being pushed to viewers of the web page.
For reasons of privacy it would be of advantage to provide a user with an option to block tracking, if he prefers not to be tracked. However, the challenge to providing such an option is that when a web browser opens a web page, the browser generally does not recognize those portions of the page that relate to tracking; and even if the browser were to recognize such portions, the browser would need a mechanism in place to block them.
<script id=″js-set-epic-spec″>  (function setRefDom(win, doc, registryFile)    {var edition = ((registryFile &&registryFile.split(′_′)[0]) || ′international′).toUpperCase( ),host =doc.referrer.replace(/{circumflex over ( )}http(?:s)?\:\/\/([\w\-\.]+).*$/i,′$1′).toLowerCase( );    win[edition] = win[edition] || { };win[edition].adTargets =window[edition].adTargets || { };    if (host.search(/{circumflex over ( )}([\w\-]+\.)*money\.cnn\.com$/) >= 0)      {win[edition].adTargets.refdom = ‘money’;}    else if (host.search(/{circumflex over ( )}([\w\-]+\.)*(www|us|edition|next)\.cnn\.com$/) >= 0)      {win[edition].adTargets.refdom = ′cnn′;}    else if (host === ′t.co′)      {win[edition].adTargets.refdom = ′twitter′;}    else if (host.search(/{circumflex over ( )}([\w\-]+\.)*facebook\.com$/) >= 0      {win[edition].adTargets.refdom = ′facebook′;}    else if (host.search(/{circumflex over ( )}([\w\-]+\.)*google\.\w{2,3}(\.\w\w)?$/) >= 0)      {win[edition].adTargets.refdom = ′google′;}    else      {win[edition].adTargets.refdom = ′other′;}  CNN.getRefDom = function getRefDom( )    {return win[edition].adTargets.refdom;};    if (CNN.PageParams && typeof CNN.PageParams.adkey ===′string′)      {win[edition].adTargets.adkey = CNN.PageParams.adkey;}    CNN.getAdkey = function getAdkey( ){returnwin[edition].adTargets.adkey || null;};    if(CNN.Utils.exists(CNN.contentModel.analytics.cap_topics))      {win[edition].adTargets.capTopics =CNN.contentModel.analytics.cap_topics.split(/,\s*/);}  CNN.getCapTopics = function getCapTopics( ) {var capTopics ={ },i,topics;    if (Array.isArray(win[edition].adTargets.capTopics)&&CNN.Utils.exists(win[edition].adTargets.capTopics[0])&&win[edition].adTargets.capTopics[0] !== ′no-value-set′)      {topics = win[edition].adTargets.capTopics;    for (i = 0; i < topics.length; i++)      {capTopics[topics[i]] = ′cap′;}}return capTopics;};  }  (window, document, ′cnni_homepage′));</script><script>  CNN.adTargets = {protocol: ″non-ss1″};  CNN.AdsConfig = {    enableAdLock: false,    enableGalleryAdRefresh:true,    galleryAdClicks: 4,    amazon: {″amznkey″:″3288″},    companionAdStates: [      {      ″label″:″small″,      ″minWidth″:0},      {        ″label″:″large″,        ″minWidth″:768}],    desktopSSID: ′edition.cnn.com_main_homepage′,    mobileSSID: ′edition.cnn.    com_mobile_mobileweb_homepage′,  CNN.Edition = ″international″;  CNN.EditionCookie = ″PreferredEdition″;  CNN.Features = {    enableAdsConsole: true,    enableAmazonDisplayAds: true,    enableEpicAds: true,    enableFreewheel: true,    enableGalleryAds: true,    enableGigyaLogin: true,    enableKrux: true,    enableLiveFyre: true,    enableProximic: true,    enableRubiconFastlane: true,    enableAmazonVideoAds: true,    enableChartbeat: true,    enableChartbeatMAB: true,    enableOmniture: true,    enableOptimizely: true,    enableOutbrain: true,    enableOutbrainVideoKPI: true,    enableZoneOutbrain: true,  CNN.Chartbeat ={″MABsrc″:″//static.chartbeat.com/js/chartbeat mab.js″,″src″:″//static.chartbeat.com/js/chartbeat.js″,″uid″:37612};  CNN.Host = {    assetPath: ″http://edition.i.cdn.cnn.com/.a/2.20.3″,    chrome: ″//i.cdn.cnn.com/cnn″,cssPath: ″/css/2.20.3″,    domain: ″http://edition.cnn.com″,    main: ″edition.cnn.com″,  sponsorContent: ″http://s3.amazonaws.com/cnn-sponsored-content″,    int1: ″http://edition.cnn.com″,    us: ″http://us.cnn.com″,    www: ″http://www.cnn.com″};</script>